Skin pricker blood sampling device

ABSTRACT

A skin pricker has a housing ( 1 ) for a lancet ( 5 ) which, when released from a rearward cocked position, is propelled forwards by a spring momentarily to project its tip ( 3 ). During the forward motion a peg ( 12 ) within the housing ( 1 ) passes along a slot ( 10 ) in the lancet and, just before the tip ( 3 ) projects, snaps through a neck ( 11 ) at the rear end of the slot. If the lancet ( 5 ) is then pushed back, the peg ( 12 ) cannot re-enter the slot ( 10 ): instead it wedges the lancet sideways and, before it can be re-cocked, traps the lancet behind an abutment ( 13 ) ensuring that the tip ( 3 ) cannot be re-exposed.

This invention relates to skin prickers. It is concerned with skinprickers of the kind where a lancet is pushed back in its housing to acocked position where it is held against a compressed spring. When thelancet is released the needle tip momentarily projects and thebounce-back of the lancet withdraws it into the housing. Arrangementsare made to prevent the lancet being fired again, so that it is a singleuse device and has to be discarded.

The aim of this invention is to simplify the structure by which thisre-use is prevented.

According to the present invention there is provided a skin prickercomprising an elongate housing, a lancet within the housing, springurged towards the forward end thereof, means for releasing the lancetalong a firing path from a cocked rearward position to cause momentaryprojection of its needle tip through an aperture at said forward end,and means for preventing re-exposure of the tip after such momentaryprojection, characterised in that the preventing means includes aprojection on the interior of the housing which initially co-operateswith a longitudinal channel in the lancet having a non-return rear endfor escape of the projection from the channel as the lancet tipapproaches exposure, subsequent co-operation of the projection with thelancet if re-cocking is attempted causing the lancet to be misalignedfrom the firing path.

Conveniently, the channel is formed by the gap between the main body ofthe lancet and a spring finger carried by the body and extendingrearwardly alongside it, the rear end of the finger converging towardssaid body to form a neck through which the projection can snap.

Preferably, there will be two fingers symmetrically disposed one oneither side of the body, one finger to co-operate with the projectionand the other being redundant. It will then not matter which of eitherof two ways the lancet is assembled with the housing.

The interior of the housing may have an abutment behind which the lancetis engaged when misaligned. If it is pushed back towards the cockedposition after firing, the projection acting on the outside of thefinger will urge the lancet sideways, and although the lancet may bere-cocked, if re-fired it will be blocked by the abutment.

The arrangement could be reversed, with the projection on the lancet andthe channel in the housing with its non-return end being the forward endthereof.

Preferably, a removable cap initially shrouds the tip of the lancet andextends through the aperture. It can serve as a means by which thelancet can be pushed back along the firing path from an assembledposition with its needle within the housing to the cocked position.

Another desirable feature is to have a trigger carried by the housingwith two modes of engagement with the lancet. In the first mode it canrestrain the lancet from significant forward movement from the assembledposition but allow the pushing back of the lancet, and in the secondmode it will hold the lancet in said cocked position until operation ofthe trigger releases it.

Conveniently, the lancet has a ratchet type engagement with the trigger,snapping back past a tooth on the trigger as it reaches the cockedposition. This tooth can also serve as the first mode restraint,co-operating with a projection on the lancet to stop the lancet movingforwards but, when the trigger is operated to fire the lancet, beinglifted clear of the lancet so as not to obstruct said projection as thelancet moves forward.

For a better understanding of the invention, one embodiment will now bedescribed, by way of example, with reference to the accompanyingdrawing, in which:

FIG. 1 is a diagrammatic perspective view of half a skin pricker housingwith a lancet as initially assembled therein,

FIG. 2 is a similar view but showing the lancet cocked,

FIG. 3 is a similar view but showing the lancet fired,

FIG. 4 is a similar view but showing the lancet re-cocked butimmobilised after firing, and

FIG. 5 is a perspective view of a complete skin pricker, opened out andwith the lancet in the cocked position.

The housing half 1 of the pricker of FIGS. 1 to 4 is a shallow,elongated rectangular open-topped box, the housing being completed by acomplementary half (not shown) closed over it. At one end there is asemi-circular recess 2, matched by another one in the other half tocreate an aperture through which the tip of a lancet needle willmomentarily project. Initially that tip 3 is shrouded by a needle cap 4integrally moulded with a lancet body 5 which can move longitudinallywithin the housing.

The body 5 is an elongated T-shaped block the cross portion 6 being atthe forward end and the stem 7 housing most of the needle. Alongside thestem, on each side, there is a finger 8 extending back from the rearcorners of the cross-portion 6 to terminate in tapered, inwardlyinclined tips 9. These create slots 10 which narrow at necks 11 at therear ends.

The interior of the half 1 has an upstanding peg 12 positioned offset toone side of the longitudinal centre line so that, when the lancet isinserted, it lies within one of the slots 10, near its rear end. Thecross portion 6 lies within a narrowed part of the housing which guidesthe lancet during cocking and firing. At this stage the needle tip 3,still within the cap 4, is within the housing. On the other side of thehalf 1, where the narrowed part terminates, the wall provides anundercut shoulder 13 forward of the peg 12.

With the housing complete, when the pricker is to be used the lancet ispressed back using the cap 4. It will be captured in the cocked positionof FIG. 2 by a trigger mechanism (not shown) . A spring 22, shown onlyin FIG. 1 for clarity of illustration, acting between the rear end ofthe housing and the free end of the stem 7 will then be fully compressedand the peg 12 is now towards the forward end of the slot 10.

On release, the lancet shoots forward, beyond its assembled position.When the finger tip 9 reaches the peg 12, the latter snaps through theassociated neck 11 and the FIG. 3 position is reached, with the needletip 3 projecting.

The lancet will bounce back into a safe position with the needle tip 3just inside the housing but will be arrested by the peg 12 meeting theinclined outer face of the finger tip 9, tending to wedge the associatedfinger 8 in towards the stem 7. Obviously, it cannot be re-fired in thatposition. However, it can be re-cocked but, as it is pushed back, thepeg 12, acting now on the outside of the finger 8, pushes the lancettowards the other side. The finger is fairly stiff, and as the pegapproaches its root it deflects more and more and pressure on the lancetincreases. So once the cross portion 6 passes the shoulder 13, thelancet is shifted sideways with a sudden snap to bring the corner ofthat portion 6 behind the shoulder 13 while the finger 8 straightensout, as shown in FIG. 4. The lancet may then be re-cocked, but ifre-fired it will not get past the shoulder 13.

It will thus be seen that re-use of the pricker is prevented.

FIG. 5 shows a complete pricker, opened out and with the lancet in theposition of FIG. 2 but with its cap still in place. The same referencesare used to indicate the parts equivalent to those of FIGS. 1 to 4.

The now visible complementary half 14 differs primarily from the half 1in having the trigger mechanism 15 previously referred to. This is ofthe rocker type, with an intermediate transverse web 16 carrying to therear a longitudinal arm 17 inclining slightly proud of the half 14 andto the front an inwardly hooked section 18. This will snap over andcatch a tooth 19 integrally formed with the portion 6 when the lancet ispushed back to the cocked position. The tooth 19 is duplicated on theother side of the portion 6 for the same reason the arms 8 areduplicated, while the spring 22 locates onto a knob 20 at the rear endof the lancet body 5. With the lancet in the cocked position shown, whenthe arm 17 is pressed flush with the half 14, twisting the web 16, thelancet is released and shoots forward.

The stem 7 of the lancet body has two opposed studs 21 at about itsmid-length, one of which projects towards the trigger, the other beingspare in case the lancet is fitted the other way up. Initially the stud21 will be immediately behind the hook of the trigger portion 18 and soif the user pulls the cap 4 instead of pushing it, the lancet cannotmove any significant distance forwards, and certainly not far enough toallow the peg 12 to escape through its associated neck 11. If it didthat, it would not be possible to fire the lancet properly. So the stud21 is a safety measure against the device being made prematurelyinoperative.

The stud 21 will travel just beyond the hooked section 18 when thelancet is fired, but so rapid is the movement that the user will nothave time to release the arm 17 and cause the hook to engage the stud 21as the lancet shoots forwards. The lancet will have bounced back to itsinitial position before the trigger assumes its original attitude.

This feature forms the main subject of our co-pending InternationalApplication claiming priority from British Patent Application No.0103977.5.

1. A skin pricker comprising an elongate housing having an interior andforward and rearward ends, a lancet within the housing, spring urgedtowards the forward end thereof, means for releasing the lancet along afiring path from a cocked rearward position to cause momentaryprojection of its needle tip through an aperture at said forward end,and means for preventing re-exposure of the tip after such momentaryprojection, characterised in that the preventing means includes aprojection on the interior of the housing or on the lancet whichinitially co-operates with a longitudinal channel in the lancet or onthe housing having a non-return rear end for escape of the projectionfrom the channel as the lancet tip approaches exposure, subsequentco-operation of the projection with the lancet if re-cocking isattempted causing the lancet to be misaligned from the firing path.
 2. Askin pricker as claimed in claim 1, characterised in that the channel isformed by a gap between a main body portion of the lancet and a springfinger carried by the body and extending rearwardly alongside it, therear end of the finger converging towards said body to form a neckthrough which the projection can snap.
 3. A skin pricker as claimed inclaim 2, characterised in that there are two fingers symmetricallydisposed one on either side of the body, one finger to co-operate withthe projection and the other being redundant.
 4. A skin pricker asclaimed in claim 1, characterized in that the interior of the housinghas an abutment behind which the lancet is engaged when misaligned.
 5. Askin pricker as claimed in claim 1, characterized in that the projectionis on the lancet and the channel is in the housing with its non-returnend being the forward end thereof.
 6. A skin pricker as claimed in claim1, characterized in that a removable cap initially shrouds the tip ofthe lancet and extends through the aperture, and also serves as a meansby which the lancet can be pushed back along the firing path from anassembled position with its needle within the housing to the cockedposition.
 7. A skin pricker as claimed in claim 1, characterized in thata trigger is carried by the housing with two modes of engagement withthe lancet, in the first mode restraining the lancet from significantforward movement from the assembled position but allowing the pushingback of the lancet, and in the second mode holding the lancet in saidcocked position until operation of the trigger releases it.
 8. A skinpricker as claimed in claim 7, characterised in that the lancet has aratchet type engagement with the trigger, snapping back past a tooth onthe trigger as it reaches the cocked position.
 9. A skin pricker asclaimed in claim 8, characterised in that said tooth also serves as thefirst mode restraint, co-operating with a projection on the lancet tostop the lancet moving forwards but, when the trigger is operated tofire the lancet, being lifted clear of the lancet so as not to obstructsaid projection as the lancet moves forwards.
 10. A skin pricker asclaimed in claim 2, characterized in that the interior of the housinghas an abutment behind which the lancet is engaged when misaligned. 11.A skin pricker as claimed in claim 3, characterized in that the interiorof the housing has an abutment behind which the lancet is engaged whenmisaligned.